It's interesting that under the current legal concept of privacy, a victim of crimes such as assault, rape etc, has to stand up in court, with the accused and their supporters present, and identify themselves and their place of residence. In a perfect world, the assailant wouldn't go round to their house and harass them, but it happens.
However, while the accused can be made to give a blood sample for identification in assault/rape cases, they can't test the accused for disease as that counts as a privacy violation. The victim has to get their own tests done to see if they have picked up anything.
happened to a friend of mine, went to help some guy passed out, got bitten and beaten up by the guy's mates.
I suppose one purpose of privacy is so that strangers with ill-intent can't use your personal info to your detriment. An extreme case:
http://www.abc.net.au/news/2011-12-01/girl27s-family-doused-in-acid-over-marraige-refusal/3705864if the gunmen didn't know where they lived, would they have been safe?